1. Field of the Invention
This invention relates to motion sensors and, more particularly, to a motion sensor disposed in close proximity to a physical body and which produces an asymmetrical output signal in response to symmetrical movement of the body.
2. Description of the Relevant Art
Many input devices are used to input data to machines. For example, keyboards, joysticks, mice, track balls, and light pens often are used to input data into a computer, usually so that operations may be selected without the necessity of keying in multiple commands on a keyboard. However, mastering the operation of such input devices is often difficult because the hand movements required to operate the device do not correspond to the visual feedback presented by the display screen of the computer.
One method and apparatus which overcomes the foregoing disadvantage is described in U.S. patent application Ser. No. 07/026,930, entitled "Computer Data Entry And Manipulation Apparatus And Method," filed on 3/17/88, now abandoned and assigned to the present assignee. That application discloses a data processing apparatus for converting gestures and positions of the hand of a physical operator into a virtual operator, such as an animated version of the hand, for manipulating virtual objects defined by a computer.
In order to accomplish the translation from the gestures and movements of the physical operator into corresponding gestures and movements of a virtual operator, flex sensors are disposed in close proximity to the physical operator for producing an output signal in response to movement of the operator's body. One example of such a flex sensor is disclosed in U.S. Pat. No. 4,542,291, issued to Thomas G. Zimmerman and assigned to the present assignee. In the embodiments disclosed, the sensors are placed on a glove for detecting the movements and gestures of the hand of the operator. Each sensor comprises a flexible tube having two ends, a reflective interior wall within the flexible tube, and a light source placed within one end of the flexible tube. A photosensitive detector placed within the other end of the flexible tube measures the amount of direct and reflected light received from the light source as the tube is bent.
Another input device used for a somewhat different purpose is described in U.S. Pat. No. 4,414,537, issued Nov. 8, 1983, to G. Grimes, entitled "Digital Data Entry Glove Interface." The Grimes patent discloses a glove with sensors for detecting the flexing of finger joints, sensors for detecting contact between various portions of the hand, and sensors for detecting the orientation of the hand. The Grimes device is used for translating discrete hand positions representing alpha-numeric characters into corresponding electrical signals.
Although the foregoing devices visually operate satisfactorily, the sensors used may give erroneous information in certain circumstances. For example, if sensors are positioned to detect bending at a junction of two members which pivot symmetrically with respect to an axis, but only movement on one side of the axis provides usable data, the computer may be unable to determine if the output produced by the sensors correspond to movement in the desired direction. That is, the sensors provide the same signal when the two members are in symmetrically opposite positions so that the computer may receive and process the data as if the data represented movement in the relevant direction when, in fact, that is not the case. Consequently, the computer is unable to translate the movements of the operator into the proper form, or the translation is performed incorrectly and the results are meaningless.